Railway track circuit apparatus



April 12, 1938. R M. GILSON 2,113,983

I RAILWAY TRACK CIRCUIT APPARATUS Filed March 31, 1937 Tb 11 H-F .536 3NVENTOR HLS' ATTO R N EY Patented Apr. 12, 1938 PATENT OFFICE RAILWAYTRACK CIRCUIT APPARATUS Robert M. Gilson, Pittsburgh, Pa., assignortoThe Union Switch 8; Signal Company, Swis vale, Pa., a corporation ofPennsylvania Application March 31, 1937, Serial No. 134,148

. 8 Claims.

My invention relates to railway track circuit apparatus and has for anobject the provision of a simple form of track circuithaving relativelyhigh shunting sensitivity. A further object of my invention is theprovision in apparatus of this character of means for providing improvedhighway crossing protection.

I shall describe one form of railway track circuit apparatus embodyingmy invention, and shall then point out the novel features thereof inclaims. 7 g p The accompanying drawing is adiagrammatic view showing oneform of trackcircuit apparatus embodying my invention, as applied to thecontrol of apparatus at a highway crossing.

Referring to the drawing, the reference char, acters E and to designatethe track rails of a stretch of railway track intersected by a highwayH. Trains may move over this stretch in either direction. Therails ofthis stretch of track are divided by insulated joints 2 to form railsections CE and EF in the upper rail and rail sections C-D and DF in thelower rail. Connected across the rail sections CE and D-F through 'acurrent limiting device 41, is a source of current 3, convenientlyillustrated as a battery. Connected across the rails at the one end ofthe stretch is a track relay Ta, and connected across the rails at theother end of the stretch is a second track relay Tb. Between railsections E-F and C--D is connected a jumper I which completes thecurrent path from source 3 to the track relays To and Th.

It will be noted that the apparatus thus far described comprises asingle track circuit which may be traced from one terminal of source 3,limiting resistor 4, wire 6, rail l, track relay Ta, rail la, jumper l,rail l, track relay Tb, rail Ia, and wire 8, to the other terminal ofthe source. By locating the rail joints 2 on opposite sides of thehighway, certain advantages with respect to the operation of the highwaycrossing apparatus are obtained. These advantages will become apparentas the description progresses.

Track relays Ta and Tb control an interlocking relay B of the usual andwell-known type. When one or the other of these track relays isdeenergized, the circuit for the respective magnet Ra or Rb of theinterlocking relay R is interrupted and an energizing circuit for asuitable highway crossing signal S becomes closed at back contact 9 or Mof the interlocking relay.

When a train moving toward the right enters section C-D, track relay Tawill be released by the train shunt and will initiate operation of the'l to la, and wire 8, back to -shown) between the armatures of magnetsBa crossing signal S through the closing of back contact 9 of magnet Rd.The signal will continue to operate even aiter the rear end of the trainhas passed the rail joint at location D because-the train shunt willcontinue to remain effective 5 across the source 3 during the time thatthe train is occupying the highway intersection, as will be obvious fromthe drawing. It will be apparent, therefore, that a warning at thecrossing will be provided during the full time that any part of thetrain occupies the highway intersection.

When the train passes beyond the rail joint at location B and completelyclears the crossing, enery will be re-applied to track relay Ta. over acircuit which may be traced from one terminal of source 3, resistor 4,wire 6, rail I, track relay Ta, rail la, jumper I, the train shunt fromrail the other terminal of the source. It should be pointed out, ofcourse, that the entry of the train into section E-F causes the trackrelay Tb to become deenergized, andthat this will usually take placebefore relay Ta' picks up. Accordingly, back contact 9a will beprevented from closing due to the presence of the well-known mechanicalinterlocking (not and Rb.

I Toavoidthe possibility of relay Ta. picking up before'relay Tbreleases, due, for example, to the passage of a fast, light weight carthrough the highway intersection, the track relays may be made slowpick-up in character to prevent prolonged operation of signals underthis condition. After the train clears section E-F, relay Tb will becomeenergized and all of the apparatus will be'restored to the condition'inwhich it is illustrated.

The operation for a train entering section E-F from right to left willbe similar in all respects to that just described. 40

The high shunting sensitivity of the track circuit herein disclosedresults from the fact that when a train enters the section, the flow ofrail current is limited not only by the limiting resistor 4 but also bythe resistance of the winding of the distant track relay.

It will be clear that the apparatus herein described is not limited tothe control of highway crossing apparatus, as the track circuitembodying my invention may be employed Wherever a track circuit of thecenter-fed type is desired. The connections 6 and 8 from source 3 andthe rail joints at locations D and E need not be staggered provided thatthe source 3 is connected across non-adjacent rail portions, such asportion CE of the upper rail and DF of the lower rail. There is,however, an advantage in staggering the rail joints at D and E eventhough the track circuit is not used in conjunction with highwaycrossing protection. This is because a single car, high speed trainpassing from one section to the other will then be able to shunt thetrack relay for the leaving end of the track circuit before releasingthe shunt on the track relay at the entering end of the track circuit,thus making more certain that the entering track relay will not pick upbefore the leaving track relay has had an opportunity to release.

An advantage of apparatus embodying my invention is that a simple formof track circuit having high shunting sensitivity has been providedwhich, when applied to highway crossing protection, provides improvedoperation of the highway crossing apparatus.

Although I have herein shown and described only one form of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from'the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of railway track intersected by ahighway, an insulated joint inone rail at one side of the highway, aninsulated joint in the other rail at the other side of the highway, saidtwo joints defining a right-hand and a left-hand track section, a

source of current connected across the two rails from one rail of saidleft-hand section to the other rail of said right-hand section, anelectrical connection joining said one rail of the: righthand sectionwith said other rail of the lefthand section, two track relays connectedrespectively across the two rails adjacent the two ends of said stretch,and highway crossing apparatus controlled by said two track relays.

2. In combination with a stretch of railway track, a first insulatedjoint in one rail of said section, a second insulated joint in the otherrail of said section and in staggered relation with said first insulatedjoint, said two joints defining a righthand and a left-hand tracksection, a source of current connected across the two rails from onerail of said left-hand section to the other rail of said right-handsection, an electrical connection joining said one rail of theright-hand section with said other rail of the left-hand section, twotrack relays connected respectively across the two rails adjacent thetwo ends of said stretch, and signaling apparatus controlled by said twotrack relays.

3. A track circuit comprising, in combination, a section of railwaytrack, a first insulated joint in one rail of said section, a secondinsulated joint in the other rail of said section, means for impressinga track voltage across the two rails of said section on opposite sidesof. said two insulated joints, means for electrically connecting the tworails on the remaining sides of said two insulated joints, a first trackrelay receiving energy from the two rails to the left of said twoinsulated joints, and a second track relay receiving energy from the tworails to the right of said two insulated joints.

4. A track circuit comprising, in combination,-

a section of railway track divided by an insulated joint in one rail andan insulated joint in the other rail to form a left-hand and aright-hand rail section, means for impressing a track voltage from onerail of. said left-hand section to the other rail of said right-handsection, means for electrically connecting said one rail of theright-hand section with said other rail of the left-hand section, afirst track relay receiving energy from said left-hand rail section, anda second track relay receiving energy from said right-hand rail section.

5. In combination, a section of railway track, an insulated jointdividing one rail of said section into a first and a second railportion, an insulated joint dividing the other" rail of said sectioninto a third and a fourth rail portion, an electrical connection betweensaid second and said third rail portions, two track relays one for eachend of said section, a source of current; and a track circuit for saidsection including said source, said connection, said four rail portions,and said two track relays all in series.

6. In combination, a section of railway track, a first insulated jointdividing one rail of said section into a first and a second railportion, a second insulated joint in staggered relation with said firstinsulated joint and dividing the other rail of said section into a thirdand a fourth rail portion, an electrical connection between said secondand said third rail portions, two track relays one for each end of saidsection, a source of current; and a track circuit for said .sectionincluding said source, said connection,

said four rail portions, and said two track relays all in series.

7. In combination with a stretch of railway track over which traffic maymove in either direction and a highway intersecting said track section,an insulated joint in one rail at one side of the highway, an insulatedjoint in the other rail at the other side of the highway, said twojoints defining a right-hand and a left-hand track section, means forimpressing a track voltage across the two rails from one rail of saidleft-hand section to the other rail of said right-hand section, meansfor electrically connecting said one rail of the right-hand section withsaid other rail of the left-hand section, a first track relay receivingenergy from the rails at one end of said stretch, a. second track relayreceiving energy from the rails at the other end of said stretch, anddirectional means controlled by said two track relays.

8. In combination with a stretch of railway track intersected by ahighway, an insulated joint in one rail at one side of the highway, aninsulated joint in the other rail at the other side ofthe highway, saidtwo joints defining a right-hand and a left-hand track section, a sourceof current connected across the two rails from one rail of saidleft-hand section to the other rail of said right-hand section, anelectrical connection between said one rail of the right-hand sectionwith said other rail of the left-hand section, two track relays eachreceiving energy from. the rails at the respective end of said stretch,an interlocking relay, and circuits for said interlocking relaycontrolled by said two track relays.

ROBERT M. GILSON.

